How Is an MRI Different From a CT Scan?
How a CT Scan Works
A CT (computed tomography) scan takes a series of X-ray images as the scanner rotates around you. A computer combines them into cross-sectional slices, and some exams can also be shown in 3D. Because CT captures images in seconds, it’s especially useful when your doctor needs answers quickly.
How an MRI Works
An MRI (magnetic resonance imaging) scan uses a strong magnetic field and radio waves to read signals from the water and fat in your body. Different tissues send different signals, which is why MRI is so good at showing the difference between healthy and injured soft tissue. To learn more about MRI safety, read Do MRI Scans Use Radiation?
Is MRI or CT Better? It Depends on the Body Part
Neither test is better overall. Each one is better at answering certain questions, so your doctor will choose based on your symptoms and the area that needs a closer look. Here’s how that choice often works.
Brain and Head
CT is often used first after a head injury or a suspected stroke because it quickly shows bleeding and skull fractures. MRI gives a more detailed look at brain tissue and is often preferred for conditions such as multiple sclerosis, brain tumors and headaches that come with other symptoms, such as changes in vision, balance or memory.
Spine and Back Pain
MRI is usually the first choice for back or neck pain with numbness, tingling or weakness because it shows spinal discs, nerves and the spinal cord. CT is helpful for bone detail, fractures and patients who can’t have an MRI. If neither gives a clear answer, a myelogram pairs contrast dye with CT for a closer look at the spinal canal and nerve roots. Learn more in Does an MRI Show Nerve Problems? [link when live].
Joints and Sports Injuries
MRI is the standard test for torn ligaments, tendons, cartilage and muscles in the knee, shoulder, hip, wrist and ankle. CT may be used for complex fractures or to help plan joint surgery.
Chest and Lungs
CT is the preferred test for the lungs. It can show small nodules, pneumonia, blood clots in the lungs and other chest conditions. American Health Imaging also offers low-dose CT lung cancer screening for eligible adults with a history of smoking.
Abdomen and Pelvis
Both tests are common here. CT is often used first for abdominal pain, appendicitis, diverticulitis and kidney stones because it’s fast and shows these problems clearly. MRI is often used for a closer look at the liver, pancreas, uterus, ovaries and prostate, or to better understand something found on an ultrasound or CT.
Emergencies and Injuries
CT is the go-to test in emergencies because it’s fast. If you have sudden, severe symptoms such as chest pain, signs of a stroke or a major injury, go to the emergency room rather than scheduling outpatient imaging.
Radiation: How Do MRI and CT Compare?
MRI doesn’t use ionizing radiation. CT does, but in small, carefully controlled doses.
At American Health Imaging, low-dose CT technology adjusts the dose to your body size and the area being scanned, keeping exposure as low as possible while still producing clear images. Both MRI and CT can be used safely in children when a doctor decides imaging is needed.
How Contrast Dye Differs for MRI and CT
Some exams use contrast dye to make certain tissues, blood vessels or areas of inflammation easier to see. MRI and CT use different types:
- CT contrast is iodine-based and usually given through an IV. Some abdominal and pelvic exams also use a contrast drink. You may feel brief warmth or a metallic taste during the injection.
- MRI contrast is gadolinium-based and given through an IV.
Many MRI and CT exams don’t need contrast at all, and your doctor’s order will say whether yours does. Tell your imaging team if you have kidney disease or diabetes, take metformin, are pregnant or have had a reaction to contrast before.
Scan Time, Noise and Comfort
CT is faster. Most CT scans take about 5 to 15 minutes, and the scanner is an open ring, so you’re never fully enclosed. MRI takes longer, and most exams last 30 to 60 minutes. At many AHI locations, faster scanning MRI technology reduces many scan times to as little as 8 minutes, which can make a big difference if you’re in pain. MRI scanners also make loud tapping sounds, so you’ll be given earplugs or headphones.
If tight spaces make you anxious, let us know when you schedule. Most AHI locations offer wide-bore MRI, and open MRI is available at select centers.
Does an MRI or CT Scan Cost More?
CT scans usually cost less than MRIs because they’re faster and use less complex equipment. Your final cost depends on the body area, whether contrast is used and your insurance plan.
Where you get your scan matters too. American Health Imaging offers imaging at up to 60% less than hospital imaging and is in-network with 99% of major insurance plans. You can also call your nearest center for a cost estimate before your appointment.
Why Your Doctor Might Order Both
Sometimes one test leads to the other. A CT might find something that needs a closer look with MRI, or an MRI might be followed by a CT to check bone detail before surgery. That doesn’t mean the first test missed something. Each test answers different questions, and together they give your doctor a more complete picture. If you’re not sure why a test was ordered, talk to your doctor about imaging.
Schedule Your MRI or CT Scan With American Health Imaging
Your doctor will choose the test that best fits your symptoms. Once you have a referral, American Health Imaging makes the next step easy. A board-certified, subspecialized radiologist reads your exam, and you’ll receive a Scanslated® report by text within 48 hours after your report is finalized. It uses plain language and diagrams to help you understand your results.
Same-day appointments are available, extended and weekend hours are offered at select locations and we have a 97% patient satisfaction rating.
Request an appointment or find a location near you.